CVE-2026-51616 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWanIeCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain LAN addressing and DHCP configuration information via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in TOTOLINK T6 firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the device's web management interface. Specifically, the flaw resides in the getWanIeCfg function, which is invoked when processing requests directed to the /cgi-bin/cstecgi.cgi endpoint. This component is responsible for retrieving configuration details related to Wide Area Network settings and associated local network parameters. The core technical deficiency lies in the absence of proper authentication checks or session validation before executing this specific function. Consequently, any actor with network connectivity to the router can interact with this interface without providing valid credentials, effectively bypassing the intended security boundaries designed to protect sensitive configuration data from unauthorized access.
From a technical perspective, the exploitation vector involves sending a crafted POST request to the specified CGI script. Unlike many web applications that require an active session token or login cookie for administrative functions, this particular endpoint fails to verify the identity of the requester prior to returning data. This oversight allows unauthenticated attackers to query the system and extract detailed information regarding LAN addressing schemes and Dynamic Host Configuration Protocol (DHCP) configurations. The ability to retrieve DHCP configuration is particularly significant as it reveals the range of IP addresses assigned by the router, which can be used for further network mapping or denial-of-service attacks targeting specific hosts within the local area network.
The operational impact of this vulnerability extends beyond simple information disclosure. By obtaining LAN addressing and DHCP details, an attacker gains a comprehensive understanding of the internal network topology. This knowledge facilitates more sophisticated subsequent attacks, such as IP spoofing, ARP poisoning, or targeted denial-of-service campaigns against specific devices within the subnet. Furthermore, exposure of configuration parameters may aid in identifying other potential weaknesses or default settings that could be leveraged for deeper compromise. The lack of authentication requirement means that this vulnerability is easily exploitable remotely over the internet if port 80 or 443 is exposed, posing a severe risk to home and small business networks where such routers are commonly deployed as gateways.
This flaw aligns with CWE-269, which classifies Improper Privilege Assignment, specifically highlighting cases where access control checks are missing for critical functions. It also relates closely to CWE-862, the Missing Authorization vulnerability, as the system fails to enforce policy regarding who is allowed to perform specific actions or view certain data. In terms of offensive security frameworks, this behavior corresponds to techniques found in MITRE ATT&CK under Initial Access and Discovery phases, particularly those involving web application scraping or exploitation for information gathering. The ease of exploitation via standard HTTP POST requests underscores the urgency of addressing this issue, as automated tools can readily scan for such misconfigurations across large segments of internet-connected devices.
Mitigation strategies must prioritize immediate patching to a firmware version that corrects the access control logic within the getWanIeCfg function. Until an official update is available, network administrators should consider restricting access to the router's management interface by placing it behind additional authentication layers or firewall rules if possible. Disabling remote management features entirely is also recommended for most residential users, as this eliminates the attack surface from external networks. Regularly auditing configuration settings and ensuring that only necessary services are exposed can further reduce the risk of exploitation. Ultimately, enforcing strict input validation and mandatory session verification on all administrative endpoints is essential to prevent similar vulnerabilities in future firmware releases.